With the preponderance of precision motion detection using optical encoders, industries demand a high resolution motion encoder with interpolation of between 10× and 1000×. With such high resolution demands, conventional open-loop optical motion encoders are not able to meet these specifications. Typically, conventional encoders suffer from assorted problems such as device aging, process and temperature drifts, contamination on optical surfaces, and other problems that limit the resolution of the encoders.
A conventional approach to compensate for these problems is to use binning options, device trimming, or firmware calibrations. However, each of these implementations has some disadvantages. In general, these solutions increase testing complexity, increase die size, increase die cost, and/or require additional bond pads.
Another conventional approach to compensate for these problems is to use a signal conditioning feedback system. A signal conditioning feedback system detects and evaluates signals within the encoder and performs compensations to account for variations in the detected signals. However, conventional signal conditioning feedback systems also have disadvantages. For example, some conventional systems implement a low pass filter to extract the direct current (DC) component from an input signal. For low frequency applications (e.g., 1 KHz to 100 KHz), particularly for motion detection, the low pass filter uses a very big passive capacitor or active filters. Additionally, many conventional signal conditioning feedback systems are sensitive to process variations, if they are implemented without device trimming.